Boston Police said the woman, who had been seen by witnesses arguing with a man, was stabbed in front of 15 Midland Street around 4 p.m.

The mother, in her 20s, still pushing her stroller, reached the Savin Scoops ice cream shop on Savin Hill Avenue before she collapsed, screaming "Call 911."

"She was stabbed pretty badly," Savin Scoops owner Joe Conway told the Boston Herald. "There was blood all over the stroller." Witnesses believe the woman, who was stabbed four times, knew her attacker.

The baby, who Conway said appeared to be about 1 year old, was not injured.

Police said the woman was taken to the hospital with life-threatening injuries.

Lawyers for Boston Marathon bomber Dzkokhar Tsarnaev rested their case in his federal death penalty trial Tuesday after presenting a brief case aimed at showing his late older brother was the mastermind of the 2013 terror attack.